Association redirection method and device

ABSTRACT

Provided is a stream control transmission protocol (SCTP) association redirection method and apparatus, a non-transitory storage medium, and a processor. The method includes following: A first network element determines whether an initial trigger message of a UE traffic flow transmitted by a second network element is received, where the initial trigger message of the UE traffic flow is transmitted through an SCTP association on which the UE currently sticks or through a new SCTP association after the second network element redirects the UE to the new SCTP association; and the first network element performs an SCTP association redirection on the UE in response to a determination result.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 16/764,825,filed May 15, 2020, which is filed under 35 U.S.C. § 371 as the U.S.National Phase of Application No. PCT/CN2018/116112, filed Nov. 19,2018, which claims priority to Chinese Patent Application No.201711147185.9 filed Nov. 17, 2017, the disclosures of which areincorporated herein by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to the field of communications and, forexample, relates to an association redirection method and apparatus.

BACKGROUND

In 3rd Generation Partnership Project (3GPP), control signaling betweencommunication network elements adopts multiple stream controltransmission protocols (SCTP) as underlying transmission protocols toensure the reliability of signaling transmission. Moreover, theestablishment of an SCTP association between a pair of network elementsis supported in the latest 3GPP standard.

However, in some application scenarios or abnormal situations, a userstuck in a certain association or a certain network element needs tomigrate to a new association, so as to ensure the continuity of the userservice.

According to a conclusion of the current standard conference, an accessand mobility management function (AMF) may redirect user equipments(UEs) on an SCTP association to SCTP associations within the same AMF orSCTP associations within another AMF. However, it is not clear how theAMF redirects these UEs to new associations. Additionally, the standardalso does not specify other methods for redirecting a user of anassociation between network elements (for example, between a NextGeneration NodeB-Centralized Unit (gNB-CU) and a Next GenerationNodeB-Distributed Unit (gNB-DU)) that support multiple associations.

SUMMARY

The embodiments of the present disclosure provide an SCTP associationredirection method and apparatus, to at least solves the problem in therelated art of how to implement an association redirection of a userbetween network elements that support multiple associations, and theproblem in the related art of how to perform the association redirectionon the UE from any association in the first network element to anassociation of another first network element in a scenario where asecond network element is connected to multiple first network elements.

An embodiment of the present disclosure provides an associationredirection method. The method includes that: a first network elementdetermines whether an initial trigger message of a UE traffic flowtransmitted by a second network element is received, where the initialtrigger message of the UE traffic flow is transmitted through an SCTPassociation on which the UE currently sticks or through a new SCTPassociation after the second network element redirects the UE to the newSCTP association; and the first network element performs an SCTPassociation redirection on the UE in response to a determination result.

Another embodiment of the present disclosure further provides anassociation redirection apparatus, which is applied to a first networkelement. The apparatus includes a processor, and a memory, wherein thememory stores processor-executable programs, and the processor executesthe programs to perform the method of any embodiment described above.

Another embodiment of the present disclosure further provides anon-transitory storage medium. The storage medium includes storedprograms. The programs, when executed, perform the method of anyembodiment described above.

Another embodiment of the present disclosure further provides aprocessor. The processor is configured to execute program. The programs,when executed, perform the method of any embodiment described above.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of hardware of a mobile terminal of anassociation redirection method according to an embodiment of the presentdisclosure;

FIG. 2 is a flowchart of an association redirection method according toan embodiment of the present disclosure;

FIG. 3 is a flowchart of another association redirection methodaccording to an embodiment of the present disclosure;

FIG. 4 is a flowchart of another association redirection methodaccording to an embodiment of the present disclosure;

FIG. 5 is a processing diagram of redirecting a UE to another SCTPassociation of the same network element according to an embodiment ofthe present disclosure;

FIG. 6 is a processing diagram of redirecting a UE to an SCTPassociation of another network element of the same type according to anembodiment of the present disclosure;

FIG. 7 is a processing diagram illustrating that a first network elementimplicitly redirects a UE to another association of the first networkelement according to an embodiment of the present disclosure;

FIG. 8 is a processing diagram of changing a transport associationthrough an initial message of a second network element according to anembodiment of the present disclosure;

FIG. 9 is a processing diagram illustrating that a first network elementtriggers a steady-state UE to redirect the steady-state UE to anotherassociation of the first network element according to an embodiment ofthe present disclosure;

FIG. 10 is a processing diagram of mode two illustrating that a firstnetwork element triggers a steady-state UE to redirect the steady-stateUE to another association of the first network element according to anembodiment of the present disclosure;

FIG. 11 is a processing diagram illustrating that a first networkelement triggers a steady-state UE to redirect the steady-state UE toanother association between network elements according to an embodimentof the present disclosure;

FIG. 12 is a schematic diagram of transmission networking of a NextGeneration NodeB (gNB) and multiple associations of AMFs according to anembodiment of the present disclosure;

FIG. 13 is a cooperation diagram illustrating that an AMF triggers, in aflow, a gNB to redirect the gNB to an SCTP within a specified networkelement according to an embodiment of the present disclosure;

FIG. 14 is a cooperation diagram illustrating that an AMF triggers, in aflow, a gNB to redirect the gNB to another AMF according to anembodiment of the present disclosure;

FIG. 15 is a cooperation diagram illustrating that an AMF triggers a UEon a steady-state association to redirect the UE between associationswithin the AMF according to an embodiment of the present disclosure;

FIG. 16 is a cooperation diagram illustrating that an AMF redirects a UEon an association to a specified association within the AMF according toan embodiment of the present disclosure;

FIG. 17 is a processing and cooperation diagram illustrating that an AMFtriggers a UE on an association to perform a cross-AMF redirection onthe UE according to an embodiment of the present disclosure;

FIG. 18 is a cooperation diagram illustrating that a gNB triggers, in anuplink message, a UE to perform an association redirection on the UEaccording to an embodiment of the present disclosure;

FIG. 19 is a processing and cooperation diagram of a UE redirectiontriggered by a gNB according to an embodiment of the present disclosure;

FIG. 20 is a block diagram of an association redirection apparatusaccording to an embodiment of the present disclosure;

FIG. 21 is a block diagram of another association redirection apparatusaccording to an embodiment of the present disclosure; and

FIG. 22 is a block diagram of another association redirection apparatusaccording to an embodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure will be described hereinafter in detail withreference to the drawings and in conjunction with the embodiments. Ifnot in collision, the embodiments described herein and the featuresthereof may be combined with each other.

The terms “first”, “second” and the like in the specification, claimsand preceding drawings of the present disclosure are used fordistinguishing between similar objects and are not necessarily used fordescribing a particular order or sequence.

Embodiment One

A method embodiment provided by the embodiment one of the presentdisclosure may be executed in a mobile terminal, a computer terminal orother similar computing apparatuses. Taking the method executed in themobile terminal as an example, FIG. 1 is a block diagram of hardware ofa mobile terminal of an association redirection method according to anembodiment of the present disclosure. As shown in FIG. 1 , a mobileterminal 10 may include one or more (only one is shown in FIG. 1 )processors 102 (each processor 102 may include, but is not limited to amicro controller unit (MCU), a field-programmable gate array (FPGA) oranother processing apparatus), a memory 104 configured to store data,and a transmission device 106 with a communication function. It may beunderstood by those skilled in the art that the structure shown in FIG.1 is only illustrative, and not intended to limit the structure of theelectronic apparatus described above. For example, the mobile terminal10 may further include more or fewer components than the componentsshown in FIG. 1 , or may have a configuration different from theconfiguration shown in FIG. 1 .

The memory 104 may be configured to store software programs and modulesof application software, for example, program instructions/modulescorresponding to the association redirection method in the embodiment ofthe present disclosure. The processor 102 executes the software programsand modules stored in the memory 104 to perform multiple functionalapplications and data processing, that is, to perform the precedingmethod. The memory 104 may include a high-speed random access memory,and may further include a nonvolatile memory such as one or two magneticstorage apparatuses, flash memories or other nonvolatile solid-statememories. In some examples, the memory 104 may include memories that areremotely disposed with respect to the processor 102, and these remotememories may be connected to the mobile terminal 10 via a network.Examples of the preceding network include, but are not limited to, theInternet, an intranet, a local area network, a mobile communicationnetwork and combinations thereof.

The transmission device 106 is configured to receive or transmit datavia a network. Examples of such a network may include a wireless networkprovided by a communication provider of the mobile terminal 10. In anexample, the transmission device 106 includes a network interfacecontroller (NIC). The NIC may be connected to other network devices viaa base station and thus can communicate with the Internet. In anexample, the transmission device 106 may be a radio frequency (RF)module. The RF module is configured to communicate with the Internet ina wireless way.

The description “between network elements” mentioned in the embodimentof the present disclosure may refer to “between a gNB and an AMF”,“between a gNB-CU and a gNB-DU”, “between an evolved NodeB (eNB) and amobility management entity (MME)” and the like. When a UE accesses, abase station selects an appropriate transport association for the UEaccording to information carried by the UE during access, and the UEkeeps stuck to this association during the subsequent process. This canavoid unnecessary context migration and synchronization, and achieve thebest processing performance and user experience. In the embodiment ofthe present closure, in some application scenarios or abnormalsituations, a certain association may be broken due to a failure of anunderlying network or be shut down according to requirements of networkmaintenance, all associations of a network element are out of servicedue to maintenance or a failure of the network element or other factors,a certain SCTP has a high load, or other factors.

Based on the preceding mobile terminal, an embodiment of the presentdisclosure provides an association redirection method. FIG. 2 is aflowchart of an association redirection method according to anembodiment of the present disclosure. As shown in FIG. 2 , the methodincludes steps described below.

In step 202, a first network element determines a trigger mode fortriggering an association redirection of a UE.

In step 204, the first network element performs the associationredirection on the UE according to the determined trigger mode.

According to the preceding steps, the first network element determinesthe trigger mode for triggering the association redirection of the UE,and the first network element performs the association redirection onthe UE according to the determined trigger mode. This solves the problemin the related art of how to implement an association redirection of auser between network elements that support multiple associations, andthe problem in the related art of how to perform the associationredirection on the UE from any association in the first network elementto an association of another first network element in a scenario where asecond network element is connected to multiple first network elements.The association redirection is performed on the user by determining thetrigger mode for triggering the association redirection of the UE, sothat load imbalance between multiple associations or network elements isavoided, and the effect on the user experience when a certainassociation or network element fails is avoided.

In an embodiment, the trigger mode includes a procedure messagetriggering redirection mode, and a redirection mode of a UE in a flowsteady state.

In an embodiment, under the condition that the trigger mode is theprocedure message triggering redirection mode, the step in which thefirst network element performs the association redirection on the UEaccording to the determined trigger mode includes one of steps describedbelow.

The first network element receives an initial trigger message of atraffic flow of the UE transmitted by the second network element, andfeeds back a redirection request to the second network element throughan association receiving the initial trigger message. The redirectionrequest is used for enabling the second network element to redirect theUE to a new association. The second network element transmits aredirection acknowledgement through the new association to update anassociation of the UE to the new association.

The first network element receives the initial trigger message of thetraffic flow of the UE transmitted by the second network element, andtransmits the redirection acknowledgement to the second network elementthrough the new association. The redirection acknowledgement carriesprompt information that the first network element has redirected the UEto the new association. Alternatively, the first network elementreceives the initial trigger message of the traffic flow of the UEtransmitted by the second network element, and updates associationinformation of the UE to the association receiving the initial triggermessage.

In an embodiment, before the step in which the first network elementtransmits the redirection acknowledgement to the second network elementthrough the new association, the method further includes a stepdescribed below.

The first network element redirects the UE to the new associationaccording to a predetermination or a traffic factor.

In an embodiment, after the step in which the first network elementupdates the association information of the UE to the associationreceiving the initial trigger message, the method further includes astep described below.

The first network element replies a redirection acknowledgement to thesecond network element.

The redirection acknowledgement is used for indicating that theassociation information of the UE has been updated.

In an embodiment, the redirection request includes at least one of auser application layer identifier, a redirection target or anunprocessed-message information element.

The user application layer identifier is configured to identify a userto be redirected.

The redirection target includes a target association and/or a targetinterface. When the target association is valid, a user is redirected toanother association of the network element. When the target interface isvalid, the user is redirected to an association of a network element ofthe same type as the first network element.

The unprocessed-message information element carries an unprocessed flowtrigger message delivered by the second network element to the firstnetwork element.

In an embodiment, the redirection acknowledgement includes at least oneof a user application layer identifier, an old-network-elementglobal-application-identifier information element or anunprocessed-message information element.

The user application layer identifier is configured to identify a userto be redirected.

The old-network-element global-application-identifier informationelement carries a global application identifier of a network element towhich an original association of the UE belongs before the UE isredirected.

The unprocessed-message information element carries an unprocessedmessage delivered by the second network element to the first networkelement.

In an embodiment, under the condition that the trigger mode is theredirection mode of the UE in the flow steady state, the step in whichthe first network element performs the association redirection on the UEaccording to the determined trigger mode includes steps described below.

The first network element determines a redirection type for redirectingthe UE to a new association.

The first network element performs the association redirection on the UEaccording to the determined trigger mode and the redirection type.

In an embodiment, the redirection type includes the followings:redirecting the UE on an association of the first network element to anew association within the first network element, and redirecting the UEto a network element of the same type as the first network element.

In an embodiment, under the condition that the redirection type is:redirecting the UE on the association of the first network element tothe new association within the first network element, the first networkelement determines the redirection type for redirecting the UE to thenew association in one of manners described below.

The first network element determines to redirect a part of UEs on ahigh-load association to a new low-load association.

The first network element determines an association to be shut down on abasis of maintenance or traffic requirements, and redirects all UEs onthe association to be shut down to the new association.

In an embodiment, under the condition that the redirection type is:redirecting the UE to the network element of the same type as the firstnetwork element, the first network element determines the redirectiontype for redirecting the UE to the new association in one of mannersdescribed below.

The first network element detects that a load of the first networkelement is greater than a preset value, and determines to redirect theUE of the first network element to the network element of the same typeas the first network element.

The first network element determines, on the basis of maintenance ortraffic requirements, to shut down or stop the first network element,and redirects the UE of the first network element to the network elementof the same type as the first network element.

In an embodiment, the step in which the first network element performsthe association redirection on the UE according to the determinedtrigger mode and the redirection type includes steps described below.

The first network element selects a UE on the association and to beredirected to the new association within the first network element.

The first network element transmits a redirection command to the secondnetwork element through the new association. The redirection commandincludes an information list of the UE to be redirected to the newassociation and indicates a redirection between associations within thenetwork element. The redirection command is used for enabling the secondnetwork element to redirect the UE to the new association.

In an embodiment, the step in which the first network element performsthe association redirection on the UE according to the determinedtrigger mode and the redirection type includes the step described below.

Under the condition that the first network element selects a targetassociation for redirecting while selecting the UE to be redirected,association information of the UE is updated while the redirectioncommand is transmitted to the second network element.

In an embodiment, the step in which the first network element performsthe association redirection on the UE according to the determinedtrigger mode and the redirection type includes steps described below.

The first network element selects the information list of the UE to beredirected to the new association, and selects a target association towhich the UE is redirected.

The first network element allocates the UE to the target association,and transmits a redirection indication through the target association.The redirection indication carries the information list of the UE onwhich the association redirection is completed.

In an embodiment, the step in which the first network element performsthe association redirection on the UE according to the determinedtrigger mode and the redirection type includes a step described below.

The first network element transmits a redirection command to the secondnetwork element. The redirection command carries an information list ofthe UE to be redirected to the network element of the same type as thefirst network element. The redirection command is used for indicatingthe UE to be performed an association redirection between networkelements.

In an embodiment, the redirection command includes redirection interfaceinformation and/or redirection association information

In an embodiment, the redirection interface information includes one ofa redirection interface all-user information element, a redirectioninterface part-user information element, a user application identifierlist information element or a target network element identifier listinformation element.

When the redirection interface all-user information element is valid,all users in the first network element are redirected.

When the redirection interface part-user information element is valid, apart of users in the first network element is redirected.

The user application identifier list information element is configuredto carry identifier information of a user to be redirected and includesone or more pieces of user identifier information.

The target network element identifier list information element specifiesa candidate target network element for redirecting. If the targetnetwork element identifier list is not specified, the second networkelement selects, according to a load, the network element of the sametype as the first network element to serve as the candidate targetnetwork element.

In an embodiment, the redirection association information includes aredirection association all-user information element, a redirectionassociation part-user information element, a user application identifierlist information element, a target association list information elementand a target network element identifier.

When the redirection association all-user information element is valid,all users on the association are redirected.

When the redirection association part-user information element is valid,a part of users on the association is redirected.

The user application identifier list information element is configuredto carry identifier information of a user to be redirected on theassociation and includes one or more pieces of user identifierinformation.

The target association list information element is valid when anassociation redirection within the network element is performed. Atarget association list carries information of a candidate targetassociation.

When the target network element identifier is configured to be valid, anassociation redirection between network elements is performed and anetwork element specified by a target network element identifier list inthe target association list is used as a candidate network element.

In an embodiment, the redirection indication includes at least one of aredirected-user list information element or an old-network-elementapplication-identifier information element.

The redirected-user list information element carries an information listof a user redirected to an association and includes one or more piecesof user identifier information.

The old-network-element application-identifier information element isconfigured to request UE context information from an old network elementby a new network element in a scenario where a user is performed across-network element redirection.

Embodiment Two

Another embodiment of the present disclosure further provides anassociation redirection method. FIG. 3 is a flowchart of anotherassociation redirection method according to an embodiment of the presentdisclosure. As shown in FIG. 3 , the method includes steps describedbelow.

In step 302, a second network element transmits an initial triggermessage of a traffic flow of a UE to a first network element.

In step 304, the second network element receives a redirection requestfed back by the first network element through an association receivingthe initial trigger message, and redirects the UE to a new associationaccording to the redirection request. Alternatively, the second networkelement receives a redirection acknowledgement transmitted by the firstnetwork element through the new association, where the redirectionacknowledgement carries prompt information that the first networkelement has redirected the UE to the new association.

In an embodiment, before the step in which the second network elementredirects the UE to the new association according to the redirectionrequest, the method further includes steps described below.

Under the condition that the redirection request carries an identifierof the new association, the second network element matches the newassociation according to the identifier of the new association.

Under the condition that the redirection request does not carry theidentifier of the new association, the second network element decidesand determines the new association.

In an embodiment, the step in which the second network element matchesthe new association according to the identifier of the new associationincludes steps described below.

Under the condition that the identifier of the new association indicatestransport network layer address (TNLA) information of the newassociation, the second network element matches the new associationaccording to the TNLA information.

Under the condition that the identifier of the new association indicatesa global application identifier of the new network element, the secondnetwork element selects a target network element for redirectingaccording to the global application identifier of the new networkelement, and selects the new association among transport associationsestablished with the target network element.

Under the condition that the identifier of the new association indicatesa new association information element, the second network elementselects an association other than a current association within the firstnetwork element as the new association.

In an embodiment, after the step in which the second network elementredirects the UE to the new association according to the redirectionrequest, the method further includes a step described below.

The second network element transmits a redirection request once throughthe new association, or feeds back a redirection acknowledgement throughthe new association.

In an embodiment, the redirection request further carries a userapplication layer identifier for identifying the UE.

In an embodiment, the redirection request includes at least one of auser application layer identifier, a redirection target or anunprocessed-message information element.

The user application layer identifier is configured to identify a userto be redirected.

The redirection target includes a target association and/or a targetinterface. When the target association is valid, the user is redirectedto another association of the network element. When the target interfaceis valid, the user is redirected to an association of a network elementof the same type as the first network element.

The unprocessed-message information element carries an unprocessed flowtrigger message delivered by the second network element to the firstnetwork element.

In an embodiment, the redirection acknowledgement includes at least oneof a user application layer identifier, an old-network-elementglobal-application-identifier information element or anunprocessed-message information element.

The user application layer identifier is configured to identify a userto be redirected.

The old-network-element global-application-identifier informationelement carries a global application identifier of a network element towhich an original association of the UE belongs before the UE isredirected.

The unprocessed-message information element carries an unprocessedmessage delivered by the second network element to the first networkelement.

Embodiment Three

Another embodiment of the present disclosure further provides anassociation redirection method. FIG. 4 is a flowchart of anotherassociation redirection method according to an embodiment of the presentdisclosure. As shown in FIG. 4 , the method includes steps describedbelow.

In step 402, a second network element receives a redirection commandtransmitted by a first network element through a new association. Theredirection command includes an information list of a UE to beredirected to the new association.

In step 404, the second network element performs an associationredirection on the UE according to the redirection command.

In an embodiment, the step in which the second network element performsthe association redirection on the UE according to the redirectioncommand includes a step described below.

Under the condition that the redirection command is used for indicatinga redirection between associations within a network element, the secondnetwork element selects one or more new associations for the UE in theredirection command according to the redirection command, and allocatesthe UE to be redirected to the one or more selected new associations.

In an embodiment, the method further includes a step described below.

The second network element constructs a redirection indication accordingto the one or more selected new associations and the allocated UE, andtransmits the redirection indication to the first network elementthrough the one or more associations. The redirection indication is usedfor the first network element to update association information for theUE.

In an embodiment, the method further includes a step described below.

Under the condition that the redirection command is used for indicatingthe redirection between associations within the network element andfurther carries a target association to which the UE is redirected, thesecond network element updates association information of the UEaccording to the information list of the UE carried in the redirectioncommand and the target association while receiving the redirectioncommand.

In an embodiment, the step in which the second network element performsthe association redirection on the UE according to the redirectioncommand includes steps described below.

Under the condition that the redirection command is used for indicatingthe redirection between associations within the network element, thesecond network element receives a redirection indication transmitted bythe first network element through a target association to which the UEis allocated. The redirection indication carries an information list ofthe UE on which the association redirection has been completed.

The second network element updates, according to the redirectionindication, an association of the user to an association receiving theredirection indication.

In an embodiment, the method further includes steps described below.

Under the condition that the redirection command is used for indicatingthat the UE is to be performed an association redirection betweennetwork elements, the second network element receives the redirectioncommand. The redirection command carries an information list of a UE tobe redirected to a network element of the same type.

The second network element selects the new association according toassociation load information of the network element which is connectedto the first network element and has the same type as the first networkelement, and allocates the UE to the new association according to theinformation list of the UE.

In an embodiment, the method further includes a step described below.

The second network element transmits a redirection indication to thenetwork element of the same type as the first network element. Theredirection indication is used for enabling the network element of thesame type as the first network element to redirect the UE to the newassociation. The redirection indication carries an information list ofthe allocated UE and an application identifier of the first networkelement which serves the UE.

In an embodiment, the method further includes a step described below.

Under the condition that the first network element determines a targetnetwork element or a target association while selecting the UE to beredirected and is capable of notifying the target network element toupdate association information of the UE, the second network elementabandons transmitting the redirection indication to the target networkelement.

In an embodiment, the redirection command includes redirection interfaceinformation and/or redirection association information

In an embodiment, the redirection interface information includes one ofa redirection interface all-user information element, a redirectioninterface part-user information element, a user application identifierlist information element or a target network element identifier listinformation element.

When the redirection interface all-user information element is valid,all users in the first network element are redirected.

When the redirection interface part-user information element is valid, apart of users in the first network element is redirected.

The user application identifier list information element is configuredto carry identifier information of a user to be redirected and includesone or more pieces of user identifier information.

The target network element identifier list information element specifiesa candidate target network element for redirecting. If the targetnetwork element identifier list is not specified, the second networkelement selects, according to a load, the network element of the sametype as the first network element to serve as the candidate targetnetwork element.

In an embodiment, the redirection association information includes aredirection association all-user information element, a redirectionassociation part-user information element, a user application identifierlist information element, a target association list information elementand a target network element identifier.

When the redirection association all-user information element is valid,all users on the association are redirected.

When the redirection association part-user information element is valid,a part of users on the association is redirected.

The user application identifier list information element is configuredto carry identifier information of a user to be redirected on theassociation and includes one or more pieces of user identifierinformation.

The target association list information element is valid when anassociation redirection within the network element is performed. Atarget association list carries information of a candidate targetassociation.

When the target network element identifier is configured to be valid, anassociation redirection between network elements is performed and anetwork element specified by a target network element identifier list inthe target association list is used as a candidate network element.

In an embodiment, the redirection indication includes at least one of aredirected-user list information element or an old-network-elementapplication-identifier information element.

The redirected-user list information element carries an information listof a user redirected to an association and includes one or more piecesof user identifier information.

The old-network-element application-identifier information element isconfigured to request UE context information from an old network elementby a new network element in a scenario where a user is performed across-network element redirection.

The embodiments of the present disclosure support a method forredirecting one or more users accessing to a certain association to anew SCTP association between network elements that support multipletransport associations, and a method for redirecting a user to a newassociation between associations of multiple network element clusters.This avoids load imbalance between multiple SCTP associations, andavoids performance problems or user disconnection caused by out ofservice (including out of service caused by artificial intervention) ofa part of associations or network elements to affect the userexperience. When a network element at one end decides to redirect a UEto another SCTP association, different implementation schemes areadopted according to the current flow state of the UE, whether the newassociation after the redirection belongs to the same network element asthe old association before the redirection, and the number of UEs to beredirected.

A redirection triggered by a procedure messages includes steps describedbelow.

The first network element receives a flow trigger message (referring tothe first message that triggers a new traffic flow) of the UE. The firstnetwork element may determine to redirect the UE to another associationaccording to the current association state.

If the UE is redirected to another association within the first networkelement or an association within the network element of the same type asthe first network element, the first network element may reply a“redirection request” message to the second network element through anSCTP association receiving the message. The “redirection request”message includes an initial request message previously received by thesecond network element. Additionally, the “redirection request” messagemay carry “new association identifier” information (such as a TNLA ofthe new association, or a global application identifier of the newnetwork element if the UE is expected to be redirected to anothernetwork element). Alternatively, the “redirection request” message doesnot carry a related information element of the new association, and thetarget association is decided by the second network element. Moreover,the message further carries “user application layer identifier”information for identifying a user between network elements.

FIG. 5 is a processing diagram of redirecting a UE to another SCTPassociation of the same network element according to an embodiment ofthe present disclosure. FIG. 6 is a processing diagram of redirecting aUE to an SCTP association of another network element of the same typeaccording to an embodiment of the present disclosure. As shown in FIGS.5 and 6 , the second network element selects the new association for theUE according to the “redirection request” message. The method includesthe following steps: if the new association identifier informationindicates TNLA information of the new association, the SCTP associationis matched according to the TNLA information; if the new associationidentifier information indicates the global application identifier ofthe new network element, the target network element for redirecting isfirstly selected by using this information, and then an appropriate SCTPassociation is selected among transport associations established betweenthe second network element and the target network element; if the newassociation identifier information indicates a new associationinformation element, another association within the first networkelement is selected, and then a message carried in the redirectionmessage is retransmitted once or a redirection acknowledge message isreplied through the newly selected association. In the case of thecross-network element redirection, the message carries a globalapplication identifier of the first network element before theredirection to convenient for the new network element fetching thecontext of the user. In an embodiment, n in the drawings represents aserial number, such as a serial number of the SCTP association, or aserial number of the first network element.

Additionally, FIG. 7 is a processing diagram illustrating that a firstnetwork element implicitly redirects a UE to another association of thefirst network element according to an embodiment of the presentdisclosure. As shown in FIG. 7 , to reduce the two interaction delayscaused by the preceding method, after the first network elementprocesses the flow trigger message, the first network element replies aresponse message to the second network element through the newassociation to implicitly change the transport association of the UE.When the second network element receives the response message throughthe new association, it is indicated that the first network elementredirects the UE to this association, so the second network element alsoredirects the association information of the UE to this association.

FIG. 8 is a processing diagram of changing a transport associationthrough an initial message of a second network element according to anembodiment of the present disclosure. As shown in FIG. 8 , it is assumedthat the UE has accessed to a certain association. When a new flow isstarted, a network element initiating the flow transmits a flow requestmessage (or a one-way indicating message) through the new association,and redirects the UE to this association. A network element receivingthe message also redirects the UE to the new association receiving themessage.

In addition to the preceding application procedure message, theembodiment of the present disclosure also relates to two user-levelmessages: the “redirection request” message and the “redirectionacknowledge” message. The “redirection request” message includes one ormore pieces of information: a “user application layer identifier”, a“redirection target” or an “unprocessed-message” information element.

The “user application layer identifier” is configured to identify a userto be redirected.

The “redirection target” includes a “target association” and/or a“target interface”.

When the “target association” is valid, it is indicated that the user isredirected to another association of the network element. Thisinformation element carries an optional “target TNLA” informationelement, that is, a target association address. If the message carriesthe “target TNLA” information element, the user is redirected to aspecified association, and otherwise, the user is redirected to anotherassociation of the first network element.

When the “target interface” is valid, it is indicated that the user isredirected to the association of the network element of the same type asthe first network element. This information element carries an optional“target-network-element global application identifier”. If the messagecarries the “target-network-element global application identifier”, theuser is redirected to an association of a specified network element, andotherwise, the second network element selects an appropriate associationof the network element of the same type as the first network element forthe user.

The “unprocessed-message” information element carries an unprocessedflow trigger message delivered by the second network element to thefirst network element.

The “redirection acknowledgement” message includes one or more pieces ofinformation: a “user application layer identifier”, an“old-network-element global-application-identifier” information elementor an “unprocessed-message” information element.

The “user application layer identifier” is configured to identify a userto be redirected.

The “old-network-element global-application-identifier” informationelement carries a global application identifier of a network element towhich an original association of the UE belongs before the UE isredirected.

The “unprocessed-message” information element carries an unprocessedflow trigger message delivered by the second network element to thefirst network element.

Under the condition that UEs are in a flow steady state redirection, theflow steady state means that the UEs have established contexts in thefirst network element and the second network element and have no trafficflow to process when the redirection is to be triggered. In this state,it is expected to redirect a part of users or all users to otherassociations in scenarios described below.

The first network element discovers, through monitoring or trafficmeans, that some associations of the first network element have highloads, and thus expects to redirect a part of the users on theseassociations to low-load associations.

For maintenance or traffic requirements, it is expected to shut down acertain transport association and redirect all users on this associationto other associations.

If the first network element has a high load, it is expected to redirectthe user of the first network element to another network element of thesame type.

For maintenance or traffic requirements, it is expected to shut down orstop the first network element and redirect the user to another networkelement.

FIG. 9 is a processing diagram illustrating that a first network elementtriggers a steady-state UE to redirect the steady-state UE to anotherassociation of the first network element according to an embodiment ofthe present disclosure. As shown in FIG. 9 , if a UE on a certainassociation of the first network element is redirected to anotherassociation within the first network element, the first network elementselects the UE on the certain association and to be redirected toanother association, transmits a “redirection command” message to asecond network element through the certain association, where themessage includes an information list of the UE to be redirected toanother association, and indicates a redirection between associationswithin the first network element. The second network element receivesthe “redirection command” message, selects an appropriate SCTPassociation for the UE in the message. The second network element mayselect multiple new associations for the UE in the list, and allocatesthe UE to be redirected to the selected association. The second networkelement constructs a “redirection indication” message according to theselected new association and the allocated UE, and transmits the“redirection indication” message to the first network element throughthe corresponding association. The first network element updatesassociation information of the corresponding UE according to a UE listin the redirection indication message.

If the first network element has selected a target association forredirecting while selecting the UE to be redirected, associationmessages of these UEs to be redirected are updated while the“redirection command” message is transmitted to the second networkelement. When receiving the “redirection command” message, the secondnetwork element updates, according to the target association forredirecting and the UE to be redirected in the message, the associationinformation of the UE to be redirected. Thus, it is not necessary totransmit messages in steps 4 and 4 a of FIG. 9 , and the step in whichthe first network element updates the association information of the UEis adjusted to be after step 1.

Additionally, FIG. 10 is a processing diagram of mode two illustratingthat a first network element triggers a steady-state UE to redirect thesteady-state UE to another association of the first network elementaccording to an embodiment of the present disclosure. As shown in FIG.10 , that the first network element performs a migration on a user of anassociation to another association of the first network element may beimplemented through the following manner: the first network elementdirectly transmits a redirection indication message through a targetassociation, where the redirection indication message carries a mode forredirecting to the association. Firstly, the first network elementselects a list of users to be redirected to other associations, andselects target associations to which these users may be redirected.Then, these users are allocated to candidate associations according toan appropriate way, a redirection indication message is constructed andthe redirection indication message carries a list of users allocated toassociations, and the redirection indication message is transmitted tothe second network element through the corresponding association. Ifmultiple target associations are selected, a respective message istransmitted through each candidate association. Finally, the secondnetwork element modifies, according to the received respectiveredirection indication message, the corresponding transport associationof the user to be an association receiving the message.

FIG. 11 is a processing diagram illustrating that a first networkelement triggers a steady-state UE to redirect the steady-state UE toanother association between network elements according to an embodimentof the present disclosure. As shown in FIG. 11 , if UEs are redirectedto other network elements of the same type as the first network element,such as first network elements x and n in FIG. 11 , the first networkelement selects an information list of the UEs to be redirected to othernetwork elements, constructs a redirection message and transmits theredirection message to a second network element. The message indicatesthat these UEs are to be performed a redirection between networkelements. If these UEs belong to multiple associations of first networkelement 1, the first network element may summarize these UEs in onemessage to transmit, or may summarize theses UEs according to differentassociations and then transmit respective redirection messages throughdifferent associations to the second network element. The second networkelement receives the redirection request message, selects appropriatenew associations according to the list of the UEs to be redirected andload information of associations of other network elements having thesame type as the first network element and connected to the secondnetwork element, allocates the UEs to these new associations, andconstructs a respective redirection indication message for eachcandidate new association to carry an information list of the allocatedUEs and application identifiers of first network elements which servethe UEs, so that target network element may correctly fetch the context.Other examples for the first network element are included, such as afirst network element x and a first network element n receiveredirection response messages, fetch the context information of the UEsaccording to the first network element application identifiers in themessages and UE information in the information lists, and complete theassociation redirection operations for the UEs.

Similarly, if the first network element determines a target networkelement or a target association while selecting the UE to be redirectedand is capable of notifying the target network element to updateassociation information of the UE, the second network element does notneed to transmit an association redirection indication message to notifythe first network element, and it is not necessary to perform steps 4and 4 a of FIG. 11 .

In this scenario, the embodiment of the present disclosure relates totwo messages: a “redirection command” message and a “redirectionindication” message.

The “redirection command” message is used for the first network elementrequiring the second network element to redirect a corresponding user toanother association.

The “redirection command” message includes “redirection interface”information and/or “redirection association” information.

The “redirection interface” information includes a “redirectioninterface all-user” information element, a “redirection interfacepart-user” information element, a “user application identifier list”information element and a “target network element identifier list”information element.

When the “redirection interface all-user” information element is valid,all users in the first network element are redirected.

When the “redirection interface part-user” information element is valid,a part of users in the first network element is redirected.

The “user application identifier list” information element is configuredto carry identifier information of a user to be redirected, and mayinclude one or more pieces of user identifier information.

The “target network element identifier list” information element is anoptional call and specifies a candidate target network element forredirecting. If the “target network element identifier list” is notspecified, the second network element selects the network element of thesame type as the first network element to serve as the candidate targetnetwork element according to a load.

The “redirection association” information includes a “redirectionassociation all-user” information element, a “redirection associationpart-user” information element, a “user application identifier list”information element, a “target association list” information element anda “target network element identifier”.

When the “redirection association all-user” information element isvalid, it is indicated that all users on the association are redirected.

When the “redirection association part-user” information element isvalid, it is indicated that a part of users on the association areredirected.

The “user application identifier list” information element is configuredto carry identifier information of a user to be redirected and may andmay include one or more pieces of user identifier information.

The “target association list” information element is valid when anassociation redirection within the network element is performed. Atarget association list carries information of a candidate targetassociation.

When the target network element identifier is configured to be valid, anassociation redirection between network elements is performed, and anetwork element specified by a network element identifier list in thetarget association list is used as a candidate network element.

The “redirection indication” message is used for the second networkelement to indicate information of a user in the first network elementto be redirected to the association. The “redirection indication”message includes one or more pieces of a “redirected-user list”information element or an “old-network-element application identifier”information element.

The “redirected-user list” information element carries an informationlist of a user redirected to the association and includes one or morepieces of user identifier information.

The “old-network-element application identifier” information element isconfigured to request UE context information from an old network elementby a new network element in a scenario where a user is performed across-network element redirection.

According to the embodiments of the present disclosure, the problem thata UE is redirected from an association to another association betweenmultiple SCTP associations connected to multiple network elements of thesame type, as well as between network elements that establish multipleSCTP association is solved, so as to implement load balance betweenassociations. The user can be dynamically migrated to a new associationwithout interrupting user services when the association is out ofservice or a network element is out of service, so that the networkrobustness and availability are improved. Thus, it is supported that theon-demand addition and deletion of associations and flexible scaling ofnetwork element instances are implemented in a native cloud environmentof the fifth generation network (5G).

The embodiments of the present disclosure relate to selection processesfor an association within a network element and for an associationbetween network elements. if the association within the network elementis selected, a group of associations with lower loads may be selectedaccording to the current load state of each SCTP association, and then afinal service association is selected from this group of associationsaccording to a respective weight factor configured by an applicationlayer to each association and in accordance with a proportional fairnessprinciple. If no weight factor is configured, a service association isselected by using a random fairness algorithm. If the association ofanother network element of the same type, a group of network elementswith lower loads is selected according to a network-element load statebetween network elements of the same type, and then a final servicenetwork element is selected according to weight factors configured bythe application layer to this group of network elements and inaccordance with a proportional fairness principle. If the applicationlayer does not configure the weight factors to network elements, aservice network element is selected by using a random fairnessalgorithm. Then, the association is selected according to the selectednetwork element and the method for selecting an association within anetwork element described above. Only one association or network elementis selected each time in the preceding process. If multiple associationsor multiple network elements are selected, the preceding process may berepeatedly performed, or multiple most appropriate network elements orassociations may be selected each time.

Example One: an AMF, in a Flow, Triggers a UE to Redirect the UE to aSpecified Association within the Network Element

FIG. 12 is a schematic diagram of transmission networking of a gNB andmultiple associations of AMFs according to an embodiment of the presentdisclosure. As shown in FIG. 12 , in the networking structure, the gNB(with gNBID 101) is connected to two AMFs (AMF 1 and AMF 2 with globalunique AMF identifiers (GUAMIs) 100 and 200, respectively), and the gNBestablishes multiple transport SCTP associations with each AMF. Threeassociations SCTP 1, SCTP 2 and SCTP 3 are established between the gNBand AMF 1, and transport layer addresses at the AMF side are TNLA 1,TNLA 2 and TNLA 3, respectively. Two associations SCTP 4 and SCTP 5 areestablished between the gNB and AMF 2, and transport layer addresses atthe AMF side are TNLA 4 and TNLA 5, respectively.

Assuming that a UE selects and accesses to association SCTP 1 throughthe gNB, if the gNB triggers a handover flow, AMF 1 instructs the gNB tochange to SCTP 2. FIG. 13 is a cooperation diagram illustrating that anAMF triggers, in a flow, a gNB to redirect the gNB to an SCTP within aspecified network element according to an embodiment of the presentdisclosure. As shown in FIG. 13 , the process includes steps describedbelow.

In step 1, the gNB transmits a HANDOVER REQUIRED message to AMF 1through SCTP 1.

In step 2, in view of the load of SCTP 1 or other factors, AMF 1 decidesto change a transport association of the UE to SCTP 2, and replies aROUTE REDIRECTION REQUEST message to the gNB through SCTP 1. The messageincludes a “UE application identifier” information element carrying agNB UE next generation application protocol (NGAP) identifier (ID) andan AMF UE NGAP ID, a “target association” information element carryingtransport address TNLA 2 of SCTP 2, and an “unprocessed-message”information element carrying the HANDOVER REQUIRED message.

In step 3, the gNB receives the ROUTE REDIRECTION REQUEST message, andconstructs a ROUTE REDIRECTION ACKNOWLEDGE message according to the “UEapplication identifier”, the “target association” information and the“unprocessed message” to carry the unprocessed-message informationelement and a user identifier before the UE is redirected. Then, the gNBselects to deliver the ROUTE REDIRECTION ACKNOWLEDGE message to AMF 1through SCTP 2 according to TNLA 2, and meanwhile, changes a subsequenttransport association of the UE to SCTP 2.

In step 4, AMF 1 receives the ROUTE REDIRECTION ACKNOWLEDGE message andupdates the transport association information of the UE, processes themessage according to the “unprocessed-message” information element and aflow processing corresponding to the message, and updates the transportassociation of the UE to SCTP 2. The AMF may change the local UEapplication identifier, AMF UE NGAP ID, during this process.

In step 5, after the gNB receives a flow response message, if the AMFchanges the UE application identifier, the gNB updates the UEapplication identifier.

Example Two: an AMF Triggers, in a Flow, a UE to Redirect the UE toanother Association within the Network Element

A networking structure is shown in FIG. 12 . An AMF triggers, in a flowtrigger message, a UE to redirect the UE to another association withinthe network element, and does not specify the association. As shown inFIG. 13 , the process flow includes steps described below.

In step 1, a gNB transmits a HANDOVER REQUIRED message to AMF 1 throughSCTP 1.

In step 2, AMF 1 decides, according to the load of SCTP 1 or otherfactors, to change the UE to another transport association within thenetwork element, and replies a ROUTE REDIRECTION REQUEST message to thegNB. The message includes a UE application identifier informationelement carrying a gNB NGAP ID and an AMF UE NGAP ID, a targetassociation information element but not specifying TNLA information ofan association , a target association information element but notspecifying TNLA information of an association and an unprocessed messagecarrying the HANDOVER REQUIRED message.

In step 3, the gNB receives the ROUTE REDIRECTION REQUEST, andconstructs a message ROUTE REDIRECTION ACKNOWLEDGE message according tothe UE application identifier, the target association information andthe unprocessed message to carry the unprocessed message and a useridentifier before the UE is redirected. Then, the gNB selects thetransport association, for example, SCTP 3, according to associationloads of SCTP 2 and SCTP 3 of the AMF, and delivers the ROUTEREDIRECTION ACKNOWLEDGE message to AMF 1 through SCTP 3, meanwhile,changes a subsequent transport association of the UE to SCTP 3.

In step 4, AMF 1 receives the ROUTE REDIRECTION ACKNOWLEDGE messagethrough SCTP 3 and updates the transport association information of theUE to SCTP 3, and processes the “unprocessed-message” informationelement according to a flow processing corresponding to the message. TheAMF may change the local UE application identifier, AMF UE NGAP ID,during this process.

In step 5, after the gNB receives a flow response message, if the AMFchanges the UE application identifier, the gNB updates the UEapplication identifier.

Example Three: an AMF Triggers, in a Flow, a UE to Redirect the UE toanother AMF

A networking structure is shown in FIG. 12 . AMF 1 triggers, in a flowtrigger message, a UE to redirect the UE to another AMF. FIG. 14 is acooperation diagram illustrating that an AMF triggers, in a flow, a gNBto redirect the gNB to another AMF according to an embodiment of thepresent disclosure. As shown in FIG. 14 , the process flow includessteps described below.

In step 1, the gNB transmits a HANDOVER REQUIRED message to AMF 1through SCTP 1.

In step 2, in view of the load of SCTP 1 or other factors, AMF 1 decidesto change the UE to another AMF, and replies a ROUTE REDIRECTION REQUESTmessage to the gNB. The message includes a UE application identifierinformation element carrying a gNB NGAP ID and an AMF UE NGAP ID, atarget interface information element but not specifying the GUAMIinformation of the AMF, and an unprocessed message including HANDOVERREQUIRED message code stream.

In step 3, the gNB receives the ROUTE REDIRECTION REQUEST message, andconstructs a ROUTE REDIRECTION ACKNOWLEDGE message according to the UEapplication identifier, the target interface information and theunprocessed message code stream to carry a user identifier before the UEis redirected, the GUAMI information of AMF 1 the unprocessed messageinformation element. Then, the gNB selects another appropriate AMFnetwork element, for example, AMF 2, according to the AMF that the gNBis currently connected to, after excluding AMF 1. After that, the gNBselects an appropriate STCP association, for example, SCTP 5, accordingto loads of transport associations SCTP 4 and SCTP 5 between AMF 2 andthe gNG or according to other factors, and delivers the ROUTEREDIRECTION ACKNOWLEDGE message to AMF 2 through SCTP 5, meanwhile,changes a subsequent transport association of the UE to SCTP 5.

In step 4, AMF 2 receives the ROUTE REDIRECTION ACKNOWLEDGE messagethrough SCTP 5 and updates the transport association information of theUE to SCTP 5, transmits a context request to AMF 1 according to theGUAMI information in the message (the message includes an applicationidentifier, such as the gNB NGAP ID and the AMF UE NGAP ID, of anoriginal AMF of the UE), and fetches context information.

In step 5, AMF 1 receives the context request of AMF 2, searches for thecontext information of the UE according to the UE application layeridentifier carried in the message, and replies a context response to AMF2.

In step 6, AMF 2 performs a corresponding flow processing according tothe “unprocessed-message” information element received in step 4. AMF 2may change the local UE application identifier, AMF UE NGAP ID, duringthis process, and reply a flow response to the gNB.

In step 7, after the gNB receives the flow response message, if the AMFchanges the UE application identifier, the gNB updates the UEapplication identifier.

The mode of fetching the context in steps 4 and 5 may be implemented byusing distributed data and other shared storage modes, which are alsowithin the scope of the embodiments of the present disclosure.

Example Four: an AMF Triggers, in a Flow, a UE to Redirect the UE to aSpecified AMF

A networking structure is shown in FIG. 12 . AMF 1 triggers, in a flowtrigger message, a UE to redirect the UE to another AMF. As shown inFIG. 14 , the process flow includes steps described below.

In step 1, a gNB transmits a HANDOVER REQUIRED message to AMF 1 throughSCTP 1.

In step 2, in view of the load of AMF 1 or other factors, AMF 1 decidesto change the UE to another AMF, for example, AMF 2, and replies a ROUTEREDIRECTION REQUEST message to the gNB. The message includes a UEapplication identifier information element carrying a gNB NGAP ID and anAMF UE NGAP ID, GUAMI information carrying a target interfaceinformation element and not specifying AMF 2, and an“unprocessed-message” information element carrying the HANDOVER REQUIREDmessage.

In step 3, the gNB receives the ROUTE REDIRECTION REQUEST message, andconstructs a ROUTE REDIRECTION ACKNOWLEDGE message according to the UEapplication identifier, the target interface information and anunprocessed message code stream to carry a user identifier before the UEis redirected, GUAMI information of AMF 1 and the “unprocessed codestream” information element. Then, the gNB selects an appropriate SCTPassociation, for example, SCTP 5, according to AMF 2 that the gNB iscurrently connected to and on the basis of loads of transportsassociations SCTP 4 and SCTP 5 between AMF 2 and the gNB and otherfactors. The gNB delivers the ROUTE REDIRECTION ACKNOWLEDGE message toAMF 2 through SCTP 5, meanwhile, changes a subsequent transportassociation of the UE to SCTP 5.

In step 4, AMF 2 receives the ROUTE REDIRECTION ACKNOWLEDGE messagethrough SCTP 5 and updates the transport association information of theUE to SCTP 5, transmits a context request to AMF 1 according to theGUAMI information in the message (the message includes an applicationidentifier, such as the gNB NGAP ID and the AMF UE NGAP ID, of theoriginal AMF of the UE), and fetches context information.

In step 5, AMF 1 receives the context request of AMF 2, searches for thecontext information of the UE according to the UE application layeridentifier carried in the message, and replies a context response to AMF2.

In step 6, AMF 2 performs a corresponding flow processing according tothe “unprocessed-message” information element received in step 4. AMF 2may change the local UE application identifier, AMF UE NGAP ID, duringthis process, and reply a flow response to the gNB.

In step 7, after the gNB receives the flow response message, if the AMFchanges the UE application identifier, the gNB updates the UEapplication identifier.

The mode of fetching the context in steps 4 and 5 may be implemented byusing distributed data and other shared storage modes, which are alsowithin the scope of the embodiments of the present disclosure.

Example Five: an AMF Triggers a Part of UEs on an Association toRedirect the Part of UEs to a Specified Association of the NetworkElement

A networking structure is shown in FIG. 12 . Due to a high load of SCTP1 and other factors, AMF 1 is to redirect a part of UEs on SCTP 1 to oneor more specified SCTP associations within the network element. FIG. 15is a cooperation diagram illustrating that an AMF triggers a UE on asteady-state association to redirect the UE between associations withinthe AMF according to an embodiment of the present disclosure. Theprocess is described below.

In step 1, AMF 1 expects to redirect a part of UEs on SCTP 1 to otherassociations of AMF 1 according to traffic, the load of SCTP 1 and otherfactors. In view of user experience performance, AMF 1 may migrate theseselected UEs to one or more associations such as SCTP 2 and SCTP 3, andconstruct a ROUTE REDIRECTION COMMAND message to instruct a gNB toredirect the users on the association to the one or more specifiedassociations. The message is filled with following information elements:a “redirection association part-user” information element, where the“redirection association part-user” information element is filled withan application layer identifier (gNB UE NGAP ID and AMF UE NGAP ID) listof the UEs to be redirected, and an “association redirection target”information element, where the “association redirection target”information element includes a transport address TNLA 2 of targetassociations SCTP 2 for redirecting and a transport address TNLA 3 oftarget associations SCTP 3 for redirecting.

In step 2, the gNB selects and updates, according to a list of the UEsto be redirected in the ROUTE REDIRECTION COMMAND message, associationinformation of the UEs to be redirected, allocates the UEs specified inthe “redirection association part-user” information element to thesecandidate associations according to the “association redirectiontarget”, constructs a respective ROUTE REDIRECTION INDICATION messagefor each candidate association, where the respective message includes alist of a user redirected to each association, and transmits therespective messages to the AMF through each association.

In step 3, the AMF receives the ROUTE REDIRECTION INDICATION message andupdates a transport association of the UE to the association receivingthe message.

Example Six: an AMF Triggers a Part of UEs on an Association to Redirectthe Part of UEs to another Association of the Network Element

A networking structure is shown in FIG. 12 . Due to a high load of SCTP1 and other factors, AMF 1 is to redirect a part of UEs on SCTP 1 toanother SCTP association (which may be multiple associations) within thenetwork element. As shown in FIG. 15 , the process is described below.

In step 1, AMF 1 expects to redirect a part of UEs on SCTP 1 to anotherassociation of AMF 1 according to traffic, the load of SCTP 1 and otherfactors, and constructs a ROUTE REDIRECTION COMMAND message to instructa gNB to redirect the specified UE on the association to anotherassociation within the network element. The message is filled withfollowing information elements: a “redirection association part-user”information element, where the “redirection association part-user”information element is filled with an application layer identifier (gNBUE NGAP ID and AMF UE NGAP ID) list of the UEs to be redirected, and an“association redirection target” information element, where the“association redirection target” information element does not specifyassociation information, and the gNB decides a candidate association.

In step 2, the gNB selects and updates, according to a list of the UEsto be redirected in the ROUTE REDIRECTION COMMAND message, theassociation information of the UEs to be redirected, selects a list ofcandidate associations, such as SCTP 2 and SCTP 3, for redirectingaccording to transport associations established between the gNB and AMF1, allocates the UEs to be redirected to these candidate associations,allocates the UEs specified by the “redirection association part-user”to these candidate associations, constructs a respective ROUTEREDIRECTION INDICATION message for each candidate association, where therespective message includes a list of a user redirected to eachassociation, and transmits the respective message to the AMF througheach association.

In step 3, the AMF receives the ROUTE REDIRECTION INDICATION message andupdates a transport association of the UE to the association receivingthe respective message.

Example Seven: an AMF Triggers All UEs on an Association to Redirect allthe UEs to a Specified Association of the Network Element

A networking structure is shown in FIG. 12 . Due to the maintenance forSCTP 1 and other factors, AMF 1 is to redirect all UEs on SCTP 1 to oneor more specified SCTP associations within the network element. As shownin FIG. 15 , the process is described below.

In step 1, AMF 1 expects to redirect all UEs on SCTP 1 to otherassociations of AMF 1 In view of the user experience, AMF 1 may migratethese UEs to be redirected to multiple associations such as SCTP 2 andSCTP 3, and construct a ROUTE REDIRECTION COMMAND message to instruct agNB to redirect all users on the association to the specifiedassociations. The message is filled with following information elements:a “redirection association all-user” information element, and an“association redirection target” information element, where the“association redirection target” information element includes atransport address TNLA 2 of target associations SCTP 2 for directing anda transport address TNLA 3 of target associations SCTP 3 for directing.

In step 2, the gNB selects all users on the association for redirectingaccording to that a redirection type included in the ROUTE REDIRECTIONCOMMAND message is association for all users, allocates the UEs to beredirected to these candidate associations according to the “associationredirection target”, and constructs a respective ROUTE REDIRECTIONINDICATION message for each candidate association, where the respectivemessage includes a list of a user redirected to each association, andtransmits the respective message to the AMF through each association.

In step 3, the AMF receives the ROUTE REDIRECTION INDICATION message andupdates a transport association of the UE to the association receivingthe message.

Example Eight: an AMF Triggers All UEs on an Association to Redirect Allthe UEs to another Association of the Network Element

A networking structure is shown in FIG. 12 . Due to the maintenance forSTCP 1 and other factors, AMF 1 is to redirect all UEs on SCTP 1 toanother SCTP association (which may be multiple associations) within thenetwork element. As shown in FIG. 15 , the process is described below.

In step 1, AMF 1 expects to redirect all UEs on SCTP 1 to anotherassociation of AMF 1, and constructs a ROUTE REDIRECTION COMMAND messageto instruct a gNB to redirect all users on the association to otherassociations. The message is filled with following information elements:a “redirection association all-user” information element, and an“association redirection target” information element, where the“association redirection target” does not specify associationinformation.

In step 2, the gNB selects all users on the association for redirectingaccording to that a redirection type included in the ROUTE REDIRECTIONCOMMAND message is association for all users, and selects a list ofcandidate associations for redirecting, such as SCTP 2 and/or SCTP 3,according to transport associations established between the gNB and AMF1. The gNB allocates the UEs to be redirected to the associations in thelist of candidate associations, constructs a respective message ROUTEREDIRECTION INDICATION for each candidate association, where respectivemessage includes a list of a user to be redirected to each association,and transmits the respective message to AMF 1 through each association.

In step 3, the AMF receives the ROUTE REDIRECTION INDICATION message andupdates a transport association of the UE to the association receivingthe respective message.

Example Nine: an AMF Redirects a UE on an Association to a PpecifiedAssociation within the AMF

A networking structure is shown in FIG. 12 . Due to the load of SCTP 1,maintenance and other factors, AMF 1 is to redirect a part of UEs or allUEs on SCTP 1 to one or more specified SCTP associations within thenetwork element. FIG. 16 is a cooperation diagram illustrating that anAMF redirects a UE on an association to a specified association withinthe AMF according to an embodiment of the present disclosure. As shownin FIG. 16 , the process is described below.

In step 1, AMF 1 expects to redirect a part of UEs or all UEs on SCTP 1to another association of AMF 1 according the load of SCTP 1. In view ofthe user experience, AMF 1 may migrate these UEs to one or moreassociations such as SCTP 2 and/or SCTP 3, allocate the UEs on SCTP 1and to be redirected to SCTP 2 and/or SCTP 3 according to a load orother factors, and construct a respective ROUTE REDIRECTION INDICATIONmessage for each association, where the respective message includes anapplication layer identifier list of a user redirected to eachassociation, and the list includes a gNB UE NGAP ID and an AMF UE NGAPID. If the AMF expect to modify an AMU UE NGAP ID simultaneously, a NewAMF UE NGAP ID is carried in the list element, and the AMF transmits therespective constructed message to the gNB through each association.

In step 2, the gNB updates a transport association of the UE to theassociation receiving the respective message according to that theinformation list of the UE to be redirected to the association includedin the ROUTE REDIRECTION INDICATION message, and if the message carriesa New AMF UE NGAP ID, replaces the AMF UE NGAP ID with the New AMF UENGAP ID.

Example Ten: an AMF Triggers a Part of UEs on an Association to beRedirected to another AMF

A networking structure is shown in FIG. 12 . Due to the load of anetwork element and other factors, AMF 1 is to redirect a part of UEs onSCTP 1 to another SCTP association (which may be multiple associations)within the network element. FIG. 17 is a processing and cooperationdiagram illustrating that an AMF triggers a UE on an association toperform a cross-AMF redirection on the UE according to an embodiment ofthe present disclosure. As shown in FIG. 17 , the process is describedbelow.

In step 1, AMF 1 expects to redirect a part of UEs on SCTP 1 to anassociation of another AMF, and constructs a ROUTE REDIRECTION COMMANDmessage to instruct a gNB to redirect a part of UEs on the associationto another association. The message is filled with following informationelements: a “redirection association part-user” information element,where the “redirection association part-user” information element isfilled with an application layer identifier (gNB UE NGAP ID and AMF UENGAP ID) list of the UEs to be redirected, and an “associationredirection target” information element, where the “associationredirection target” information element does not specify network elementidentifier information.

In step 2, the gNB uses the part of UEs referred in the “redirectionassociation part-user” information element included in the ROUTEREDIRECTION COMMAND message to serve as candidate UEs to be redirected,selects, according to transport associations established between the gNBand another AMF, a list of redirection candidate associations, forexample, associations SCTP 4 and SCTP 5 of AMF 2 (where there may be oneor more AMFs and one or more associations of each AMF). The gNBallocates the candidate UEs to be redirected to the candidate in thelist of candidate associations, and constructs a respective ROUTEREDIRECTION INDICATION message for each association, where therespective message includes a list of a user redirected to eachassociation and GUAMI information is specified in an“old-network-element application-identifier” information element, andtransmits the respective message to AMF 2 through each association.

In step 3, AMF 2 receives the ROUTE REDIRECTION INDICATION message andupdates a transport association of the UE to the association receivingthe respective message, and for each user, AMF 2 requests the context ofeach UE according an application identifier of each UE and the GUAMIinformation of AMF 1.

In step 4, AMF 1 fetches the context information of the UE according toa context application identifier of the UE and replies a contextresponse to AMF 2, and meanwhile, AMF 1 clears the context informationof the UE.

In step 5, after fetching the context information of the UE, AMF 2updates association information and the application identifier of theUE, and when receiving a UE message of the gNB next time, the UE messageof the gNB still carries an application identifier of a UE allocated bythe AMF 1 side.

For the process of fetching the UE context in steps 3 and 4, the mode offetching the context through distributed database storage and the likeis also within the scope of the embodiments of the present disclosure.For the user to be redirected, the gNB may carry a new UE applicationidentifier allocated by the AMF 2 side in a message subsequentlytransmitted by AMF 2 to the gNB, and the gNB needs to update theapplication identifier of the UE in time.

Example Eleven: an AMF Triggers All UEs on an Association to RedirectAll the UEs to a Specified AMF

A networking structure is shown in FIG. 12 . Due to maintenance for SCTP1 and other factors, AMF 1 is to redirect all UEs on SCTP 1 to anotherAMF (which may be multiple associations). As shown in FIG. 17 , theprocess is described below.

In step 1, AMF 1 expects to redirect all UEs on SCTP 1 to an associationof another AMF, and constructs a ROUTE REDIRECTION COMMAND message toinstruct a gNB to redirect all users to another association. The messageis filled with following information elements: a “redirectionassociation all-user” information element, and an “associationredirection target” information element, where the “associationredirection target” information element does not specify the networkelement identifier information, for example, GUAMI of AMF 2.

In step 2, the gNB redirects all users on the association to a new AMF 2according to the ROUTE REDIRECTION COMMAND message, and selects a listof candidate associations to be redirected, for example, SCTP 4 and/orSCTP 5, according to transport associations established between the gNBand AMF 2. The gNB allocates the UEs to be redirected to theassociations in the list of the candidate associations, and constructs arespective ROUTE REDIRECTION INDICATION message for each association,where the respective message includes a list of a user redirected toeach association and GUAMI information of AMF 1 is specified in an“old-network-element application-identifier” information element. ThegNB transmits the respective message to the AMF through eachassociation.

In step 3, AMF 2 receives the ROUTE REDIRECTION INDICATION message andupdates a transport association of the UE to the association receivingthe message, and for each user, AMF 2 requests the context of each UEaccording an application identifier of each UE and the GUAMI informationof AMF 1.

In step 4, AMF 1 fetches the context information of the UE according toa context application identifier of the UE and replies a contextresponse to AMF 2, and meanwhile, AMF 1 clears the context informationof the UE.

In step 5, after fetching the context information of the UE, AMF 2updates association information of the UE and updates the applicationidentifier of the UE, and when receiving a UE message of the gNB nexttime, the UE message of the gNB still carries an application identifierof a UE allocated by the AMF 1 side.

For the process of fetching the UE context in steps 3 and 4, the mode offetching the context through distributed database storage and the likeis also within the scope of the embodiments of the present disclosure.For the user to be redirected, the gNB may carry a new UE applicationidentifier allocated by the AMF 2 side in a message subsequentlytransmitted by AMF 2 to the gNB, and the gNB needs to update theapplication identifier of the UE in time.

Example twelve: an AMF Triggers All Users of the Network Element toRedirect All the Users to another AMF.

A networking structure is shown in FIG. 12 . In view of maintenance,upgrading and other requirements, AMF 1 may be shut down to avoidaffecting UEs that have accessed to AMF 1, and the users of AMF 1 are tobe migrated to another AMF, for example, AMF 2. As shown in FIG. 17 ,the process is described below.

In step 1, AMF 1 expects to redirect the UEs that access to the networkelement to another network element of the same type, and transmits aROUTE REDIRECTION COMMAND message (that is, corresponding to an AMFstatus indication message in the standard) to the gNB. The message isfilled with following information elements: a “redirection interfaceall-user” information element and an “interface redirection target”information element, where if AMF 1 expects to redirect the UEs to aspecified AMF (that is, corresponding to a backup AMF name in thestandard) (one or more AMFs), the “interface redirection target”information element specifies network element identifier information,for example, GUAMI of AMF 2, and otherwise, the “interface redirectiontarget” information element is not filled, and the gNB autonomouslydecides a redirection target AMF. AMF 1 may select any one of multipleSCTP associations of gNB 1 to transmit the ROUTE REDIRECTION COMMANDmessage to the gNB.

If the users within AMF 1 are from multiple different gNBs, the AMFseparately transmits the ROUTE REDDIRECTION COMMAND message to each gNBonce.

In step 2, the gNB selects all users that access to AMF 1 as the usersto be redirected according to the content of the ROUTE REDIRECTIONCOMMAND message and the “redirection interface all-user” informationelement.

If the “interface redirection target” information element specifiesAMFs, candidate network elements for redirecting are selected accordingto GUAMI of the AMFs. If the “interface redirection target” informationelement does not specify the AMFs, the gNB selects other AMFs inconnections to the gNB to serve as the candidate network elementsaccording to a load or other traffic factors, and then selects candidateassociations from these candidate network elements according to theselected candidate network elements.

The users to be redirected are allocated to these candidateassociations. A respective ROUTE REDIRECTION INDICATION message isconstructed for each candidate association. A “redirected-user list”information element carries an information list of a UE allocated toeach association, where information of each UE includes an applicationlayer identifier (such as a gNB UE NGAP ID and an AMF UE NGAP ID) ofeach UE. An “old-network-element application-30 identifier” informationelement is filled with GUAMI information of an original AMF which serveseach UE, for example, GUAMI information of AMF 1. The respective messageis transmitted to a new AMF, for example, AMF 2, through each candidateassociation.

In step 3, AMF 2 receives the ROUTE REDIRECTION INDICATION message andupdates a transport association of the UE to the association receivingthe respective message, and for each UE, AMF 2 requests the context ofeach UE according to the application identifier of each UE and the GUAMIof AMF 1.

In step 4, AMF 1 fetches the context information of the UE according toa context application identifier of the UE and replies a contextresponse to AMF 2, and meanwhile, AMF 1 clears the context informationof the UE.

In step 5, after fetching the context information of the UE, AMF 2updates association information and the application identifier of theUE, and when receiving a UE message of the gNB next time, the UE messageof the gNB still carries an application identifier of a UE allocated bythe AMF 1 side.

For the process of fetching the UE context in steps 3 and 4, the mode offetching the context through distributed database storage and the likeis also within the scope of the embodiments of the present disclosure.For the user to be redirected, the gNB may carry a new UE applicationidentifier allocated by the AMF 2 side in a message subsequentlytransmitted by AMF 2 to the gNB, and the gNB needs to update theapplication identifier of the UE in time.

Example Thirteen: a gNB Triggers, in an Unlink Message, a UE to Performan Association Redirection on the UE

A networking structure is shown in FIG. 12 . Assuming that a UE hasaccessed to SCTP 1, if a gNB determines to update a service associationof the UE, the gNB may change the transport association whentransmitting an uplink message to an AMF to achieve the associationredirection. FIG. 18 is a cooperation diagram illustrating that a gNBtriggers, in an uplink message, a UE to perform an associationredirection on the UE according to an embodiment of the presentdisclosure. As shown in FIG. 18 , the process is described below.

In step 1, when the uplink message is transmitted, the gNB decides tochange the association of the UE from SCTP 1 to another association, thegNB selects an appropriate association for the UE, where the associationmay be another association of AMF 1 or an association of another AMF,and the gNB delivers the message through the newly selected association.

In step 2, when an AMF receives the message through the new association,it is regards that the gNB decides to update the transport associationof the UE, thus the AMF updates a transport association of the UE to theassociation receiving the message. In an embodiment, the AMF fetches thecontext from the AMF to which the original association serving the UEbelongs.

Example Fourteen: a UE Redirection Triggered by a gNB

A networking structure is shown in FIG. 12 . A gNB may expect to migratea UE that accesses to a certain association or a certain AMF to anotherassociation or another AMF. FIG. 19 is a processing and cooperationdiagram of a UE redirection triggered by a gNB according to anembodiment of the present disclosure. As shown in FIG. 19 , the processis described below.

In step 1, the gNB selects corresponding transport associations for UEs(there may be one or more UEs) to be redirected, constructs a ROUTEREDIRECTION INDICATION message, where the message carry a “redirecteduser list” that includes information (gNB UE NGAP ID and UMF UE NGAP ID)of these selected UEs to be redirected, and if a selected user changesthe AMF, the message carries an “old-network-elementapplication-identifier” information element that includes GUAMIinformation of the original AMF which serves the UE. Then, the gNBdelivers the message through target associations for redirecting.

In step 2, an AMF receives the ROUTE REDIRECTION INDICATION messagethrough the new associations and updates a transport association of theUE carried in the message to the association receiving the message, andif the message carries the “old-network-element application-identifier”information element, fetches context information of the UE from theoriginal AMF.

Embodiment Four

Another embodiment of the present disclosure further provides anassociation redirection apparatus, which is applied to a first networkelement. FIG. 20 is a block diagram of an association redirectionapparatus according to an embodiment of the present disclosure. As shownin FIG. 20 , the apparatus includes a determination module 202 and afirst redirection processing module 204.

The determination module 202 is configured to determine a trigger modefor triggering an association redirection of a UE.

The first redirection processing module 204 is configured to perform theassociation redirection on the UE according to the determined triggermode.

Embodiment Five

Another embodiment of the present disclosure further provides anassociation redirection apparatus, which is applied to a second networkelement. FIG. 21 is a block diagram of another association redirectionapparatus according to an embodiment of the present disclosure. As shownin FIG. 21 , the apparatus includes a transmission module 212 and afirst reception module 214.

The transmission module 212 is configured to transmit an initial triggermessage of a traffic flow of a UE to a first network element.

The first reception module 214 is configured to receive a redirectionrequest fed back by the first network element through an associationreceiving the initial trigger message, and redirect the UE to a newassociation according to the redirection request; or receive aredirection acknowledgement transmitted by the first network elementthrough the new association, where the redirection acknowledgementcarries prompt information that the first network element has redirectedthe UE to the new association.

Embodiment Six

Another embodiment of the present disclosure further provides anassociation redirection apparatus, which is applied to a second networkelement. FIG. 22 is a block diagram of another association redirectionapparatus according to an embodiment of the present disclosure. As shownin FIG. 22 , the apparatus includes a second reception module 222 and asecond redirection processing module 224.

The second reception module 222 is configured to receive a redirectioncommand transmitted by a first network element through a newassociation. The redirection command includes an information list of aUE to be redirected to the new association.

The second redirection processing module 224 is configured to perform anassociation redirection on the UE according to the redirection command.

Embodiment Seven

An embodiment of the present disclosure further provides a storagemedium. The storage medium includes stored programs. The programs, whenexecuted, perform the method of any one of the embodiments describedabove.

In an embodiment, in this embodiment, the storage medium may beconfigured to store program codes for performing steps described below.

In step 110, a first network element determines a trigger mode fortriggering an association redirection of a UE.

In step 120, the first network element performs the associationredirection on the UE according to the determined trigger mode.

In an embodiment, in this embodiment, the storage medium may further beconfigured to store program codes for performing steps described below.

In step 210, a second network element transmits an initial triggermessage of a traffic flow of a UE to a first network element.

In step 220, the second network element receives a redirection requestfed back by the first network element through an association receivingthe initial trigger message, and redirects the UE to a new associationaccording to the redirection request.

Alternatively, the second network element receives a redirectionacknowledgement transmitted by the first network element through the newassociation. The redirection acknowledgement carries prompt informationthat the first network element has redirected the UE to the newassociation

In an embodiment, in this embodiment, the storage medium may be furtherconfigured to store program codes for performing steps described below.

In step 310, a second network element receives a redirection commandtransmitted by a first network element through a new association. Theredirection command includes an information list of a UE to beredirected to the new association.

In step 320, the second network element performs an associationredirection on the UE according to the redirection command.

In an embodiment, in this embodiment, the storage medium may include,but is not limited to, a universal serial bus (USB) flash disk, aread-only memory (ROM), a random access memory (RAM), a mobile harddisk, a magnetic disk, an optical disk or another medium capable ofstoring program codes.

Embodiment Eight

An embodiment of the present disclosure further provides a processor.The processor is configured to execute programs. The programs, whenexecuted, perform the steps of the method of any one of the embodimentsdescribed above.

In an embodiment, in this embodiment, the programs are configured toperform steps described below.

In step 410, a first network element determines a trigger mode fortriggering an association redirection of a UE.

In step 420, the first network element performs the associationredirection on the UE according to the determined trigger mode.

In an embodiment, in this embodiment, the programs are furtherconfigured to perform steps described below.

In step 510, a second network element transmits an initial triggermessage of a traffic flow of a UE to a first network element.

In step 520, the second network element receives a redirection requestfed back by the first network element through an association receivingthe initial trigger message, and redirects the UE to a new associationaccording to the redirection request. Alternatively, the second networkelement receives a redirection acknowledgement transmitted by the firstnetwork element through the new association, where the redirectionacknowledgement carries prompt information that the first networkelement has redirected the UE to the new association.

In an embodiment, in this embodiment, the programs are furtherconfigured to perform steps described below.

In step 610, a second network element receives a redirection commandtransmitted by a first network element through a new association. Theredirection command includes an information list of a UE to beredirected to the new association.

In step 620, the second network element performs an associationredirection on the UE according to the redirection command.

In an embodiment, examples of this embodiment may refer to the examplesin the embodiments and implementation modes described above, which willnot be repeated here.

Apparently, those skilled in the art should know that one or moremodules of the present application or one ore more steps of the presentapplication described above may be implemented by a general-purposecomputing device, the modules or steps may be concentrated on a singlecomputing device or distributed on a network formed by two computingdevices, and in an embodiment, the modules or steps may be implementedby program codes executable by the computing devices, so that themodules or steps may be stored in a storage device and executed by thecomputing devices. In some circumstances, the illustrated or describedsteps may be executed in sequences different from those describedherein, or the modules or steps may be made into one or more integratedcircuit modules separately, or two modules or steps therein may be madeinto a single integrated circuit module for implementation. In this way,the present disclosure is not limited to any specific combination ofhardware and software.

What is claimed is:
 1. A stream control transmission protocol (SCTP)association redirection method, comprising: determining, by a firstnetwork element, whether an initial trigger message of a user equipment(UE) traffic flow transmitted by a second network element is received,wherein the initial trigger message of the UE traffic flow istransmitted through an SCTP association on which a UE currently sticksor through a new SCTP association after the second network elementredirects the UE to the new SCTP association; in response to adetermination result, performing, by the first network element, an SCTPassociation redirection on the UE.
 2. The method of claim 1, wherein inresponse to the determination result, performing, by the first networkelement, the SCTP association redirection on the UE comprises: inresponse to determining that the initial trigger message of the UEtraffic flow transmitted by the second network element is received andthe initial trigger message of the UE traffic flow is transmittedthrough the SCTP association on which the UE currently sticks,processing, by the first network element, the initial trigger message ofthe UE traffic flow, and replying, by the first network element, aresponse message to the second network element through a new SCTPassociation to redirect the UE to the new SCTP association; in responseto determining that the initial trigger message of the UE traffic flowtransmitted by the second network element is received and the initialtrigger message of the UE traffic flow is transmitted through the newSCTP association after the second network element redirects the UE tothe new SCTP association, updating, by the first network element, SCTPassociation information of the UE to the SCTP association; and inresponse to determining that the initial trigger message of the UEtraffic flow transmitted by the second network element is not receivedand the UE is in a flow steady state, performing, by the first networkelement, the SCTP association redirection on the UE according to afactor related to the first network element, wherein the flow steadystate means that the UE has established contexts in the first networkelement and the second network element and has no traffic flow toprocess.
 3. The method of claim 2, wherein after updating, by the firstnetwork element, the SCTP association information of the UE to the newSCTP association, the method further comprises: replying, by the firstnetwork element, a redirection acknowledgement to the second networkelement, wherein the redirection acknowledgement is used for indicatingthat the SCTP association information of the UE has been updated.
 4. Themethod of claim 2, wherein in response to determining that the initialtrigger message of the UE traffic flow transmitted by the second networkelement is not received and the UE is in the flow steady state,performing, by the first network element, the SCTP associationredirection on the UE according to the factor related to the firstnetwork element comprises: determining, by the first network element, aredirection type for redirecting the UE to a new SCTP associationaccording to the factor related to the first network element; andperforming, by the first network element, the SCTP associationredirection on the UE according to the redirection type.
 5. The methodof claim 4, wherein the redirection type comprises: redirecting the UEon an SCTP association of the first network element to a new SCTPassociation of the first network element; and redirecting the UE on anSCTP association of the first network element to an SCTP association ofa network element of a same type as the first network element.
 6. Themethod of claim 5, wherein the first network element determines theredirection type for redirecting the UE to the new SCTP associationaccording to the factor related to the first network element in at leastone of following manners: determining, by the first network element, theredirection type is to redirect a part of UEs on a high-load SCTPassociation of the first network element to a new low-load SCTPassociation of the first network element according to a load of the SCTPassociation of the first network element; or determining, by the firstnetwork element, an SCTP association to be shut down of the firstnetwork element on a basis of maintenance or traffic requirements, anddetermining, by the first network element, the redirection type is toredirect all UEs on the SCTP association to be shut down to a new SCTPassociation of the first network element.
 7. The method of claim 5,wherein the first network element determines the redirection type forredirecting the UE to the new SCTP association according to the factorrelated to the first network element in at least one of followingmanners: detecting, by the first network element, that a load of thefirst network element is greater than a preset value, and determining,by the first network element, the redirection type is to redirect the UEof the first network element to an SCTP association of the networkelement of the same type as the first network element; or determining,by the first network element on a basis of maintenance or trafficrequirements, to shut down or stop the first network element, anddetermining, by the first network element, the redirection type is toredirect the UE of the first network element to an SCTP association ofthe network element of the same type as the first network element. 8.The method of claim 6, wherein performing, by the first network element,the SCTP association redirection on the UE according to the redirectiontype comprises: selecting, by the first network element, a UE on theSCTP association of the first network element and to be redirected to anew SCTP association of the first network element; and transmitting, bythe first network element, a redirection command to the second networkelement through the SCTP association of the first network element toenable the second network element to redirect the UE to the new SCTPassociation of the first network element, wherein the redirectioncommand comprises an information list of the UE to be redirected to thenew SCTP association and indicates a redirection between SCTPassociations of the first network element.
 9. The method of claim 6,wherein performing, by the first network element, the SCTP associationredirection on the UE according to the redirection type comprises:selecting, by the first network element, a UE on the SCTP association ofthe first network element and to be redirected to a new SCTP associationof the first network element and the new SCTP association of the firstnetwork element, transmitting, by the first network element, theredirection command to the second network element to enable the secondnetwork element to redirect the UE to the new SCTP association of thefirst network element, and updating, by the first network element, theSCTP association information of the UE.
 10. The method of claim 6,wherein performing, by the first network element, the SCTP associationredirection on the UE according to the redirection type comprises:selecting, by the first network element, an information list of the UEon the SCTP association of the first network element and to beredirected to a new SCTP association of the first network element, andselecting the new SCTP association of the first network element to whichthe UE is redirected; and allocating, by the first network element, theUE to the new SCTP association, and transmitting, by the first networkelement, a redirection indication to the second network element throughthe new SCTP association, wherein the redirection indication carries theinformation list of the UE on which the SCTP association redirection iscompleted.
 11. The method of claim 7, wherein performing, by the firstnetwork element, the SCTP association redirection on the UE according tothe redirection type comprises: transmitting, by the first networkelement, a redirection command to the second network element to enablethe second network element to redirect the UE to an SCTP association ofthe network element of the same type as the first network element,wherein the redirection command carries an information list of the UE tobe redirected to the SCTP association of the network element of the sametype as the first network element, and the redirection command is usedfor indicating the UE to be performed an SCTP association redirectionbetween network elements.
 12. The method of claim 8, wherein theredirection command comprises at least one of redirection interfaceinformation or redirection association information.
 13. The method ofclaim 9, wherein the redirection command comprises at least one ofredirection interface information or redirection associationinformation.
 14. The method of claim 10, wherein the redirection commandcomprises at least one of redirection interface information orredirection association information.
 15. The method of claim 12, whereinthe redirection interface information comprises one of: a redirectioninterface all-user information element, wherein in a case where theredirection interface all-user information element is valid, all UEs inthe first network element are redirected; a redirection interfacepart-user information element, wherein in a case where the redirectioninterface part-user information element is valid, a part of UEs in thefirst network element is redirected; a user application identifier listinformation element, which is configured to carry identifier informationof a UE to be redirected and comprises at least one piece of UEidentifier information; or a target network element identifier listinformation element, which specifies a candidate target network elementfor redirecting, wherein in a case where the target network elementidentifier list is not specified, the second network element selects,according to a load, the network element of the same type as the firstnetwork element to serve as the candidate target network element. 16.The method of claim 12, wherein the redirection association informationcomprises: a redirection association all-user information element,wherein in a case where the redirection association all-user informationelement is valid, all UEs on the SCTP association of the first networkelement are redirected; a redirection association part-user informationelement, wherein in a case where the redirection association part-userinformation element is valid, a part of UEs on the SCTP association ofthe first network element is redirected; a user application identifierlist information element, which is configured to carry identifierinformation of a UE to be redirected on the SCTP association of thefirst network element and comprises at least one piece of UE identifierinformation; a target SCTP association list information element, whereinthe target SCTP association list information element is valid in a casewhere an SCTP association redirection within the first network elementis performed, and a target SCTP association list carries information ofa candidate target SCTP association; or a target network elementidentifier, wherein in a case where the target network elementidentifier is configured to be valid, an SCTP association redirectionbetween network elements is performed and a network element specified bya target network element identifier list in the target SCTP associationlist is used as a candidate network element.
 17. The method of claim 10,wherein the redirection indication comprises at least one of: aredirected-user list information element, which carries an informationlist of a user redirected to an association, and comprises at least onepiece of user identifier information; or an old-network-elementapplication-identifier information element, which is configured torequest UE context information from an old network element by a newnetwork element in a scenario where a user is performed a cross-networkelement redirection.
 18. A stream control transmission protocol (SCTP)association redirection apparatus, which is applied to a first networkelement and comprises: a processor, and a memory, wherein the memorystores processor-executable programs, and the processor executes theprograms to perform the method of claim
 1. 19. A non-transitory storagemedium, which comprises stored programs, wherein the programs, whenexecuted, perform the method of claim
 1. 20. A processor, which isconfigured to execute programs, wherein the programs, when executed,perform the method of claim 1.